1. Field of the Invention
The present invention relates to an ink jet recording method and a recording apparatus using this method. More specifically, it relates to an ink jet recording method using ink capable of contributing to an improvement in the color expressibility of a recorded image, and a recording apparatus using this method.
2. Description of the Prior Art
An ink jet recording method converts ink, a recording liquid, into flying droplets by various methods, and causes them to land on a material to be recorded on, such as paper, to form an image in a dot-matrix format. This method involves low noise because it is a non-contact type. Furthermore, it is capable of a high-density, high-speed recording, and does not require a special treatment, such as development or fixing, for a material to be recorded on (hereinafter referred to as a record material), such as plain paper. A recording apparatus adopting this method is suitable for mass-production, and is available for a low price. In recent years, therefore, this type of recording apparatus has found widespread use. An on-demand ink jet recording apparatus, in particular, is easily available with color printing capability, and the machine itself can be downsized and simplified. Thus, such a recording apparatus is promising in terms of a future demand. With the spread of color printing, there is a growing desire for the color expressibility of an image recorded on a record material (to be also referred to as a record sheet).
We, the inventors of this invention, proposed in Japanese Patent Application No. 259023/1994 coloring materials, such as dyes or pigments, and a liquid medium for use in a recording liquid (hereinafter referred to as ink). In this application, we used ink containing a substance having thickening properties when undergoing heat, and in a narrow sense, a temperature sensitive polymer gelling thermally reversibly at its transition temperature or above, i.e., a temperature sensitive polymer gelling at its transition temperature or above and returning to a liquid state at a temperature below the transition temperature, and a substance which begins to cloud when undergoing heat (hereinafter referred to as a substance having a cloud point). This ink showed a sharply increased viscosity on the record sheet, and stably settled on the surface, achieving an improvement in color expressibility. As a method of sharply increasing its viscosity, we proposed controlled heating of the record sheet.
However, the distance between a recording head for ejecting ink and a record sheet is as small as less than several millimeters. Thus, the mere use of the above record sheet controlled heating means results in the fact that radiant heat from the heated record sheet is passed on to the surroundings of the ink ejection orifice of the opposed recording head which is doing a record action. As a result, the surroundings of the ink ejection orifice and the inside of the ink passage are liable to undergo Increased temperatures.. Especially when the recording head is performing a record action for a long time at a position opposed to the record sheet which has been heated in a controlled manner (hereinafter referred to as controlled-heated), the temperature in the surroundings of the ejection orifice is raised to the reaction temperature of the substance having thickening properties when undergoing heat, or the substance having a cloud point that is contained in the ink. Consequently, the substance having thickening properties when undergoing heat is gelled and precipitated at the parts around the ink ejection orifice or in the ink passage, or the substance having a cloud point forms an emulsion to increase the viscosity of ink, thereby occasionally hampering the ejection of ink.
We have focused on the above-described problem, and reached the concept of an ink jet recording apparatus which involves heating a record sheet at the position of recording because of the use of the aforementioned ink, and in which a rise in the temperature in the surroundings of an ink ejection orifice of a recording head is determined by the duration of residence of the recording head above a heated record sheet, and this increased temperature is lowered before the ejection function is hampered. The object of the present invention is to propose and provide an ink jet recording method for obtaining a satisfactory recorded image using the above ink based on this concept, and a recording apparatus employing this method.
To attain this object, the ink jet recording apparatus of the present invention comprises a transport means for guiding a record material to the position of recording and discharging it after recording; a record material heating means for controlled heating the record material guided to the position of recording by the transport means to a predetermined temperature range; a recording head for ejecting ink from an ink ejection orifice toward the record material to perform recording; a head residence time measuring means for measuring the duration for which the recording head resides at a position opposed to the record material controlled-heated for recording; and a control means for controlling the duration of residence of the recording head at a position opposed to the controlled-heated record material to prevent the ejection function of the recording head from being hampered because the temperature of the surroundings of the ink ejection orifice of the recording head exceeds a temperature at which the viscosity of the substance having thickening properties when undergoing heat in the ink and/or the substance having a cloud point sharply increases.
An ink jet recording method employing this recording apparatus comprises controlled-heating a record material, fed to the recording apparatus, to a predetermined temperature range; ejecting ink from an ink ejection orifice of a recording head toward the record material fed to the recording apparatus, to perform recording; and controlling the temperature of the surroundings of the ink ejection orifice of the recording head to prevent the ejection state of the recording head from being hampered owing to the rise in the temperature of the surroundings of the ink ejection orifice of the recording head caused by radiant heat from the controlled-heated record material.
In this method, the temperature of the surroundings of the ink ejection orifice of the recording head can be controlled to lie within the predetermined range, by controlling the duration of residence of the recording head at a position opposed to the heated record material. If the recording head is adapted to be cooled by a cooling fan or a Peltier device, however, it is possible to control the temperature of the surroundings of the ink ejection orifice of the recording head to lie within the predetermined range, even if the recording head keeps residing at a position opposed to the heated record material.
According to the present invention, when ink is ejected onto the heated record material for recording, the duration for which the recording head resident in the record region is measured, with the temperature of the record material being detected. Based on the results, the surroundings of the ink ejection orifice of the recording head are cooled before the temperature of the surroundings impedes the ejection function of the recording head. Since recording is carried out using this procedure, a stable recorded image with a high degree of color expression can be obtained.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings